Currently a logging error in the form of `--- Logging error ---` happens when an error is logged in the `_on_data` helper.

Fix it by properly logging the error.

Also, treat pylint errors as errors, to avoid this problem in the future.

Can be tested by running `p2p_addrv2_relay.py` with the following example diff:

```diff
diff --git a/test/functional/test_framework/p2p.py b/test/functional/test_framework/p2p.py
index 523e1bd068..0f1eb29d13 100755
--- a/test/functional/test_framework/p2p.py
+++ b/test/functional/test_framework/p2p.py
@@ -137,7 +137,7 @@ MESSAGEMAP = {
     b"notfound": msg_notfound,
     b"ping": msg_ping,
     b"pong": msg_pong,
-    b"sendaddrv2": msg_sendaddrv2,
+    #b"sendaddrv2": msg_sendaddrv2,
     b"sendcmpct": msg_sendcmpct,
     b"sendheaders": msg_sendheaders,
     b"sendtxrcncl": msg_sendtxrcncl,

./test/functional/test_runner.py p2p_addrv2_relay

./test/functional/test_runner.py p2p_addrv2_relay